Adding these features to one's website is now easier than ever but that doesn't mean you should add it to your website. The entire Web needn't be social. The way I see it the Web is a shopping mall not a day-long concert.
At a concert, or music festival, the venue does not change - the band does. The experience does not change for the viewer no matter what band gets on stage. The audience can interact, move throughout the crowd, look to their right and tell their friend how awesome the music is, etc. The environment is the same regardless of the content. (Though I will say that some bands can completely change the feel of the place if they 're great but it doesn't change the tools available to the audience.)
At a shopping mall each store is a unique experience confined in relatively the same-sized space for each store. Wholly different experiences can sit side-by-side - an Apple store next to a Hot Topic next to a Victoria's Secret next to a JC Penny. JC Penny does not make the atmosphere inside it's store match that of Hot Topic or vice versa. Why? Because they've both chosen the experience they want to offer their shoppers.
And so should you. Just because it is easy to add Facebook, Twitter or any other host of social features to your site does not mean that you should. It simply means you have the choice. Don't get caught up in hype. But don't ignore it either. Now you have to sit back and think about the environment you want to create for your audience and decide if social is right for you. Maybe it is, maybe it isn't.
"Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should." - Ian Malcom - Jurassic Park.